UHT Sterilization Technology for Beverage with Fruit Particle

As is well known to all, beverage with fruit pulp contains rich nutrition and unique flavor so it becomes more and more popular among consumers and has promising market prospect. Limited by technology, product characteristics and other factors, many beverage manufacturing enterprises can only use sterilization pot or other sterilization method with low efficiency, which cause series of problems like low sterilization capacity and high maintenance cost.

For a long time, the advanced UHT technology, self-developed by Newamstar, can not only meet the filling requirement for various liquid product according to product characteristics, filling method, and shelf life, but also can solve a series of production problems by providing high quality product and good service.

Based on strong R&D ability and keen judgment on the market, Newamstar has made a new breakthrough in the sterilization solution field for granular beverages, which is the UHT sterilization technology.

With this technology, the sterilization treatment equipment is suitable for constant sterilization of high concentration beverage containing more than 30% pulps, such as coconut cube, tomato cube, aloe vera cube, orange, and other fruit particles. Under the condition of ensuring sterilization efficiency and product shelf life, the system can continuously reduce the damage rate caused by particle sterilization in flowing process and improve sensory index so as to improve the taste. It has advantages of high heat exchange rate, easy daily maintenance and energy-saving.

The appearance of UHT technology for fruit particleThere are two kinds of sterilization method for beverage with fruit particle. One is sterilization retort, it means after filling, the PET bottled or aluminum can product will be put in a basket and then put into the sterilization retort for spraying with high temperature water or steam; another one is using a heating pot to heat the fruit pulp in small batches before filling and then make the filling process. For the first method, the product packaging material must be high temperature resistant material, and product PH value has important impact on material cost. If the PH value is more neutral, it may need much higher sterilization temperature for the product, so the packaging material cost should be much higher. No matter using the sterilization retort or the equipment has low sterilization capacity, the processing capacity of each batch is limited and cannot supply product continuously. It needs to be replaced in the middle of production. In addition, when the materials are heated through the cooking pot, the temperature will be uneven. Sometimes the central temperature in the pot does not meet the standard, which may lead to risks such as incomplete sterilization. In addition, during the heat transfer and heating process of the materials through the pot wall, the internal surface of the cooking pot is prone to burn and scale, resulting in difficult cleaning. The general shortcomings of the above equipment gave birth to the research and development of UHT technology.

 

The research and development goal of UHT technology is to treat products with neutral pH value, and the effective concentration of particles is ≥ 30% (e.g. 30 kg pulp particles in 100 kg finished product) and the specification is ≤ 5 × 5× 5 mm square particles, which can carry out 132 ~ 137 ℃ ultra-high temperature sterilization after mixing the particles and the liquid, and maintain the sterilization time at this temperature for no less than 1s, so as to completely destroy the microorganisms and spores that can grow in the particles and the liquid, minimize the physical, chemical and sensory changes of the product, and quickly cool down to the normal temperature of 25 ~ 30 ℃, providing continuous sterilized materials for the filling equipment, so that the finished products can reach commercial sterility after filling, and can be stored, transported and sold under non refrigerated conditions.

UHT technology research and development

· After absorbing liquid for a long time, the particle is easy to swell and damage

Different particle products have a certain process of absorbing water and self-expansion, such as size ≤ 5 ×5 × 5 mm square “coconut cube”. If the particles before sterilization are immersed in the liquid for a long time, the volume will increase to the saturated volume. During the flowing process, the particles in this saturated volume state will easily dehydrate or break through the hard parts of stainless steel such as equipment pipes, valves, transfer pumps and heat exchangers, resulting in sensory and taste defects. To solve this problem, online dynamic mixing is adopted, that is, the front-end mixing system mixes as much as the back-end equipment needs according to the process requirements. The fruit pulp on-line mixing system at the front end can be set on UHT to reduce particle conveying damage caused by pipelines, conveying pumps, valves and other devices during conveying. The mixed liquid with pulp can be directly stored in the UHT buffer tank for continuous use by the back-end equipment. At the same time, the mixing system can propose two mixing ratio solutions according to the equipment investment cost, which can well control the mixing accuracy of particles and liquid.

The proportion is controlled by the flowmeter (Fig.1), the particle quantity is detected by the mass flowmeter, the liquid quantity is detected by the electromagnetic flowmeter, and then mixed by the mixer, and flows into the UHT buffer tank for temporary storage.

The mixing ratio is controlled through the volumetric tank (Fig. 2). For example, the volumetric tank has a full volume of 100L, and the mixing concentration is required to be 60%. Firstly, the 40L liquid volume is detected through the electromagnetic flowmeter, which is first input into the 100L volumetric tank, and then 60L fruit particle is added to the tank. After reaching the full volume, the tank bottom valve is opened and flows into the UHT buffer tank for temporary storage.

Selection of particle conveying pump

Many particle products will be damaged in the process of conveying through the conveying pump. Therefore, it is very important to select the appropriate conveying device. All types of delivery pumps will cause a certain damage rate to particle, including positive displacement pumps, centrifugal pumps, diaphragm pumps, etc. By checking the dimension ≤ 5×5×5mm square “coconut cube”, based on the experimental data of various types of transfer pumps, the damage rate of “coconut cube” caused by all kinds of transfer pumps was collected and analyzed. It was found that the centrifugal pump had the highest damage rate. The conventional centrifugal pump rotates at a high speed through the impeller and throws out the materials at a high speed through the action of centrifugal force, resulting in high shear force damage and impact damage, making the particles into a paste state (Fig. 3), resulting in sensory loss and unable to use. The second is the pneumatic diaphragm pump, which indirectly squeezes and pushes particles through the diaphragm in the gas squeeze pump chamber. The biggest damage reason is the soft damage after extrusion (Fig. 4). At the same time, the diaphragm pump is not suitable for high-pressure output and SIP high-temperature sterilization. The smallest damage rate is the positive displacement pump. There are many types of positive displacement pumps, including rotor pump, screw pump, twin-screw pump, etc. The rotor pump expands the volume at the pump inlet through the rotation of the rotor, and the particle materials enter the pump chamber inlet. The rotor pushes the particle materials to be transported to the pump outlet along the arc pump chamber. With the rotation of the rotor, the outlet volume decreases, and the materials are completely pushed out. The positive displacement pump can handle high concentration particle materials with high efficiency and relatively small damage rate (Fig. 5). The rotor pump with appropriate selection can meet the conditions of high-pressure output. For example, the transportation experiment of 45% concentration “coconut cube” product is carried out. When the rotating speed of the rotor pump impeller is less than 130 rpm, the transportation damage rate is less than 8%. At the same time, the pump cavity impeller is made of metal, which can be treated by the superheated water SIP sterilization process at ≤ 143 ℃ to ensure the safe production of the product.

Rotor pumps also have disadvantages. When delivering CIP low viscosity cleaning liquid which is close to pure water, the cleaning liquid will flow back to the inlet through the gap between the rotor and the pump chamber, resulting in small output flow and poor cleaning effect of the back-end supply and self-cleaning. In this case, the high-efficiency centrifugal pump can be connected in series to the conveying system as a cleaning pump, which is a series rather than a common parallel process. The disadvantage of parallel process is that the rotor pump and centrifugal pump need to be switched for interval cleaning, and the flow fluctuates greatly, so it can not be transported and cleaned at the same time. By optimizing the series cleaning process of the conveying system, the rotor pump (Fig. 6) can be selected for the conveying of production products and the centrifugal pump (Fig. 7) can be selected for cleaning. The advantages of series connection can directly provide large washing force to the impeller and pump cavity clearance of the rotor pump through the large flow cleaning fluid provided by the centrifugal pump, and provide uninterrupted large flow high-pressure cleaning liquid for the rear-end equipment through the diversion of T-type safety valve, which can meet the harsh cleaning process conditions of UHT.

 

· Particle UHT heat exchanger design

Through the establishment of data model, simulation data analysis and a large number of experimental test verification, comprehensive effective data support, combined with the summary of successful experience in the beverage equipment market for many years, as well as a large number of experiments and data analysis and sorting of drinks, Newamstar designed the flow rate of 45% concentration “coconut cube” products in the sterilization system process to be ≤ 0.7m/s, and other products even choose lower flow rates. It is found that increasing the flow rate of the system will directly produce a very high shear damage rate to the particles, so that the particles will be damaged in the transportation process, and finally lead to sensory loss and affect the taste of the product.

For the design heat exchanger of 45% concentration “coconut cube”, when the flow rate is ≤ 0.7m/s, the turbulence effect will not be ideal and the Reynolds number will decrease, which means the heat exchange efficiency will decrease. At the same time, when the particles pass through the conventional smooth tubular heat exchanger, they can not roll and turn over evenly, so that the particles can not be heated and sterilized evenly in the flow process. Therefore, the particles must be continuously turned or rolled during heat exchange and temperature rise to be heated evenly. As a result, a high-efficiency spiral tubular heat exchanger is applied to 45% concentration “coconut cube”, and its inner tube structure will be matched through the experimental database according to the heat exchange characteristics of the product to design the reasonable groove depth A and pitch B (Fig. 8). In the process of passing through this special tube, the particles spin along the spiral line direction in the inner tube along the spiral convex groove on the inner wall, and the spiral overturns and stirs, while the particle materials in the center of the inner tube are continuously replaced to the periphery during the stirring process, so that the products are evenly heated through the heat exchange process of the tube wall, so as to ensure the complete sterilization of the products in the center of the inner tube and realize the purpose of rapid temperature rise.

 

· Particle UHT system cleaning

In the process of particle UHT system, on-line CIP cleaning is an important step, which directly affects the standard of equipment production cleanliness. The standard cleaning process of UHT system is to use CIP liquid to replace equipment production materials. The cleaning medium mainly cleans the pipeline, valve and heat exchanger through the product transmission pipeline. During the flushing process of pipes, valves and heat exchangers (Fig. 9), it is relatively difficult to clean some blind areas. In addition, after conveying particle materials, it is inevitable that some fibrous tissue will accumulate on the end face of forward cleaning, so we can only increase the cleaning liquid concentration or increase the cleaning times to ensure that the cleaning is qualified. This cleaning method has the disadvantages of long cleaning time, low efficiency and large consumption of cleaning chemicals. Aiming at the problem of particle UHT cleaning, Newamstar has developed a new UHT forward and backward cleaning process (Fig. 10). The system can automatically realize the forward and backward cleaning switching through the valve switch combination, avoiding the CIP cleaning blind area, which not only reduces the human intervention in the cleaning process, improves the cleaning quality, but also reduces the repeatability and chemical consumption, and the cleaning effect is guaranteed. Moreover, it reduces the manpower investment in the production process, reduces the difficulty of production operation, saves cleaning time and production cost, improves production capacity, and meets the cleaning standard requirements of particle production line.

· UHT Sterilization temperature control accuracy

In UHT sterilization technology, when the beverage containing particles is sterilized at 132 ~ 137 ℃, the central part of the particle product shall be completely sterilized, that is, the sterilization temperature in the sterilization section shall be accurately controlled, so the temperature control accuracy of the equipment must be within ± 1 ℃ under the optimal state in order to ensure that the microorganisms and spores that can grow in particles and liquid can be completely destroyed after UHT sterilization process, and safely and effectively prolong the shelf life of product. Therefore, Newamstar has designed a “step by step heating mode of multi hot water system” (FIG. 11). The pre-sterilization temperature control section at different temperatures will be set according to the product characteristics, such as holding the temperature at 95 ~ 100 ℃ for a specific time to achieve pre-sterilization. The UHT system adjusts the steam proportional valve on the heating system through the real-time feedback of the temperature detection point in the PID control, adjust and control the inlet temperature of hot water in the pre-sterilization section, that is, the first temperature adjustment compensation. The second and third compensation temperature control points can be set according to the particularity of the product. In this way, the particle materials with constant temperature can be adjusted through the multi hot water system to enter the heat exchanger in the subsequent sterilization section for final temperature control 132 ~ 137 ℃ sterilization, and then enter the high-temperature sterilization holder for 30 ~ 60s or long-term temperature sterilization. The advantage of this process is that the multi hot water system is used for temperature control. The temperature of pre-heating and sterilization section can be controlled independently, which can effectively ensure the stability of the final end of the system. At the same time, the hot water flow of each section of the multi hot water system can be adjusted by classification, which can effectively reduce the energy consumption of equipment operation cost.

· Overcoming the problem of particle damage caused by the back pressure device at the outlet of the system

In order to ensure that the sterilization section can rise to the sterilization temperature above 100 ℃, a specific pressure must be given inside the system. Under normal pressure, the maximum temperature of the feed liquid can only be raised to 100 ℃, and some heat-resistant microorganisms and spores may not be completely eliminated. However, the conventional UHT system pressurizes the system through the action of the back pressure valve to maintain the outlet pressure of the system above 2bar, so as to effectively raise the material temperature to 132 ℃ or even higher, which requires higher outlet pressure. The principle of the back pressure valve is to pressurize the inner membrane of the valve through the gas under the rated pressure, so that the valve core in the valve is downward, the gap between the valve core and the valve seat is reduced, and the inlet pressure of the valve chamber begins to increase to form pressure holding. When the pressure on the liquid side rises to the rated pressure on the other side of the diaphragm, the valve core will be pushed open to release the excess pressure on the liquid side and maintain the pressure on the liquid side at a constant pressure. For various conventional back pressure valves, when maintaining the system pressure, the up and down adjustment process of the internal valve core is easy to cause extrusion damage to the particles in the feed liquid (Fig. 12), resulting in the lack of sense of the final product.

 

In order to meet the requirements of UHT system outlet back pressure, a special outlet pressurization system process is designed. According to the requirements of particle size and proportioning concentration in the product, a special small-diameter pipe pressurization pipe is designed at the UHT outlet, and the appropriate pipe length is selected through data verification collected from experiments. Its principle (Fig. 13) is to pressurize the system for the first time through the pipeline damper, and then cooperate with the back pressure tank at the rear end to conduct secondary pressurization and pressure regulation compensation for the outlet pressure, so as to finally realize the pressure control at the outlet of the system.

· Overcoming the problem of particle damage caused by system self circulation

During the operation of ultra-high temperature UHT system, various problems will inevitably occur, and the system can not be produced continuously, resulting in the circulating sterilization of materials in the system, and the circulating sterilization of particle materials will lead to the continuous increase of particle damage rate. The system shall ensure a sterile environment without shutdown and waiting. Once the system is shut down, CIP / SIP process will be carried out again, which will extremely waste production time and operation cost. In view of the self circulation damage of products containing particles, a set of independent circulating small water tank is configured through process optimization design (FIG. 14). The T-shaped discharge valve under the balance tank is connected with the small water tank, and a stop butterfly valve is set. The connection distance between the butterfly valve and the T-shaped valve is very short, which can effectively reduce the mixing loss of products and RO water. In case of special situation, it is only necessary to directly replace the product materials in the system with RO water in the small water tank through valve switching, and push the particle materials contained in the system into the particle mixing balance tank for temporary storage, or directly return them to the front proportioning system tank for temporary storage through the switching of return valve group, while RO water has been used to replace the particle materials for continuous circulation in UHT system, ensure the normal operation of sterile environment in the system, and solve the problem of particle erosion in the product caused by long-term circulation of particle materials by replacing the medium in the system.

In addition, the purpose of setting small water tank is to make the water source pressure more stable when the system RO water supply UHT cycle. If the RO water pipeline is directly connected, the water supply pressure will fluctuate with the opening and closing of valves at other RO water use points, resulting in out of control of UHT system pressure and temperature. The top water and water top material discharge processes before and after production are common, but in the top material process, It has to be ensured that materials in the particle mixing balancing tank will not be sucked thoroughly by the rear rotor pump in case of the vacuum pumping and causing the risk of sterilize environment destruction. Generally, experienced commissioning engineers will set a minimum protective liquid level in the particle mixing balance tank. Once it is lower than the protective liquid level, the top water and water top material process will be started. However, the protective liquid level often set has become a part of the product mixing loss. Some materials can also be saved by directly replacing the product materials in the system with RO water in the water tank.

Introduction of operation data of particle UHT technology

For example, this particle UHT equipment can process coconut milk beverage with 45% coconut concentration with the specification of the coconut pulp particles ≤5*5*5mm. The equipment can perform continuous ultra-high temperature sterilization at 132-137℃ after mixing the particles and the liquid, and maintain ultra-high temperature instantaneous sterilization for 60s at this temperature, so as to completely destroy the microorganisms and spores that can grow in the particles and the feed liquid. The physical and sensory change data of coconut particles containing particle materials after passing through three different sterilization temperatures of 132 ℃ (FIG. 15), 135 ℃ (FIG. 16) and 137 ℃ (FIG. 17) are as follows:

 

 

By summarizing the sterilization data at the above temperatures of 132 ℃, 135 ℃ and 137 ℃, a curve sample table (Fig. 18) is established. By analyzing the data curve, we find a common feature, that is, the pulp particle damage rate in the beverage increases gradually after repeated UHT sterilization. In addition, according to the data, coconut particles have been damaged during the feeding process before UHT sterilization treatment. After the first UHT sterilization treatment, the damage rate has more than doubled, while after the secondary cycle sterilization, the damage rate has increased by nearly multiple rates.

From the data, it is recommended to use the process scheme that the materials should be supplied to the back-end filling immediately after the primary sterilization treatment at 132 ℃, the damage rate is controlled within 10%, and the physical sense of the particles is relatively good; Secondly, the data analysis shows that with the continuous improvement of sterilization temperature setting, the damage rate of particles at the same stage is increasing. Under the sterilization condition of 137 ℃, the damage rate of particles at the outlet of the first sterilization is close to 13%. Therefore, once the sterilization temperature of 137 ℃ and above is used, repeated sterilization of particle materials is not recommended, but to fill immediately after one treatment.

 

By systematically analyzing the shortcomings of the current general sterilization methods for drinks containing pulp particles, and solving the key technical problems, the ultra-high temperature UHT technology is introduced into the production of drinks containing pulp particles, and a new UHT equipment suitable for drinks containing particles and neutral PH value is developed, which can not only completely destroy the microorganisms and spores that can grow in particles and feed liquid, minimize the physical, chemical and sensory changes of particles, ensure the accurate control of equipment operation parameters, provide customers with efficient and reliable product treatment method, and ensure product quality.

This is a new breakthrough in UHT sterilization technology, the pride of Newamstar technical team and the technological innovation of China’s beverage production industry. Newamstar knows that innovation will win the future. Every transformation and application of innovation achievements promote the rapid growth of subdivided categories, help users improve and stabilize their diversified layout, and bring more nutritious and healthy drinks to consumers.

Newamstar will, as always, adhere to innovation, strive to innovate, shoulder its responsibilities and mission, seize opportunities, fight a technological battle, and provide more customers with high-level scientific and technological supply. Starting from the heart, starting from China, blooming the brand charm made in China and serving global consumers, Newamstar is duty bound to go all out.